The present invention relates to molten metal discharge nozzles and in particular to discharge nozzles used in steelmaking ladles having slide gate valves for controlling the flow of molten metal from the ladle. Discharge nozzles normally comprise either gunned refractory material, or prefired refractory blocks fitted into the outlet of the ladle where molten metal is discharged. After repeated use, the abrasive nature of the molten metal causes the refractory discharge nozzles to erode to a point where they are no longer useful and they must be replaced.
Evolving improvements within the state of the art have led to the development of replaceable discharge nozzle inserts. These nozzle inserts comprise either one, or two piece prefired refractory shapes sized to fit within the bore of a ladle well block. The outside surfaces of such inserts are coated with a mortar to hold them in place within the bore. Replaceable nozzle inserts have been a significant improvement within the ladle art, and in general, they have met the needs of the industry. However, the inserts of the past are both difficult to install and replace.
During installation operations, the inserts am pushed into the discharge bore of a ladle, and excess mortar, applied to the surface of the insert, is forced outward to accumulate along the bore opening. The excess mortar builds up along the various edges of the bore opening and prevents proper seating of the nozzle insert.
Conversely, if a workman fails to apply a sufficient amount of mortar to the outside surface of a nozzle insert, gaps and bare spots are introduced into the mortar joint as the insert is pushed up into the ladle bore. Such defective motor joints provide access for the molten metal to permeate behind the nozzle insert and cause premature nozzle failure.
Finally, when these replaceable nozzle inserts become worn they require replacement. The mortar bond between the insert and the discharge bore must be broken to remove the insert. This procedure is both difficult and time-consuming, and jack hammer like tools must be used to accomplish the task. This removal operation often causes damage to the surrounding refractory lining of the ladle, and further lining repairs must be made before the ladle can be placed back into service. A further disadvantage of these past nozzle inserts is their tendency to be damaged by slide gate valve mechanisms. Requirements of the modern high production continuous caster have necessitated equipping steelmaking ladles with slide gate valves to more accurately control molten metal flow rates as the liquid steel is discharged into the caster tundish. With the increased use of these newer slide gate valves, it has been discovered that their moving parts cause damage to the refractory face of the past nozzle inserts. In order to overcome this problem, various nozzle insert designs were tried. One successful insert design included a two piece refractory/steel design where the lower steel insert portion engages the slide gate valve mechanism. However, due to its high weight, the heavy steel insert portion must provide a large surface area to enable the mortar joint to hold it in place. To provide the necessary mortar joint surface area, steel inserts of the past extend into the discharge bore area where slag sensors are normally located. This causes interference with the operation of the electromagnetic slag sensors and results in substandard product.